My wife doesn't drive much. The car is a 2017 Corolla. She drives about 3500 miles a year. A tank of gas will last her 3-6 weeks. We live in NE Arkansas and it's pretty humid much of the year. I just dawned on me this morning I should probably be adding a little fuel stabilizer to her tank when she gets gas. I told her this morning to get a half tank at a time would be better. I use TRC DZL-LENE XL/10 in my mower gas with no carb trouble. If you're wondering why that, it's because I inherited it. I also have and use MMO which I've used since 1975 so I can use it if it would be better. Should I add a taste of one of these to her tank?
Absolutely you should! I worked for a large government airport fleet for 30 years. The problems caused by stale old fuel were some of the worst to repair of all. One time I asked a mechanic I respected how long was too long for fuel and he said, gas lasted reliably for about 3 months, after that all bets were off whether the motor would run off that gas.
Problems with stale fuel could happen on the kinds of engines I maintained, because most of them spent months and sometimes years sitting idle. My job was to go around and inspect, maintain, and test the numerous small engines on X-signs, small-to-large generators, etc. And the
last thing I wanted to deal with if I could possibly avoid it, was being forced to haul something all the way back to the stop, because of a no-start caused by stale fuel! So since it was stocked by the parts room, the one I used was "Stabil". I added "Stabil" to everything with a gas engine at least once a year. (We also added some kind of anti-fungal chemicals right into our main underground diesel tanks, just before the tanker came to fill it up.). And I never had any problems with no-start on any of "my" equipment.
You might need a fuel stabilizer for your wife's car, or you might not. But for $12 a year, I think I'd just add it to the tank.